The present invention is directed to a device for controlling the level of a liquid in a container which will emit infra-red rays, the device being particularly suitable for controlling the level of molten metal in a container. More particularly, the present invention is directed to a device for measuring the height of the level in a container of a liquid which emits infra-red rays, the device providing information and having controls which can be used for conditioning said level. In accordance with preferred applications, the device is used for controlling the level of molten metal in a container in a continuous-casting ingot mould; or for controlling the level of molten metal in a pig-iron ladle, which may be independent or may be coupled to one or more ingot moulds. Other applications are possible wherever it is necessary to ascertain and perhaps to control within a suitable container the level of a liquid which will emit infra-red rays.
As is known, measurement of the level of a liquid in a container is necessary to prevent the level from deviating from certain lower or upper limits. In a continuous-casting ingot mould, where the solidifying metal is discharged continuously from the bottom while the mould is continuously being filled with liquid metal from above, the level is important with a view to maintaining, among other things, a speed such as to avoid overflowing or fracturing of or in the billet. A system for controlling such levels by means of thermocouples is known, but the system is difficult and costly to construct because the thermocouples must be installed in the ingot mould or in the container. Another known system makes use of a source of radioactive isotopes positioned on one side and cooperating with means on the other side for measuring the radioactive emissions which pass through the container. The presence or absence of the molten metal conditions the passage through the container and the variation is read by a measuring device which obtains therefrom the values required to establish the level of the liquid. However, such a system is not acceptable to industry owing to the real or hypothetical dangers inherent in every source of radioactive radiation. Moreover, installation of such a system is costly.